As a BIOS/UEFI Firmware engineer I was looking through the boot log of an OpenSuSE 12.3 system to search for error messages which might indicate failures in our UEFI Firmware.
On our VIA based system I found this one:
"mtrr: your CPUs had inconsistent variable MTRR settings"

Further researching I found that this is caused by grub2 (the grub2 used by OpenSuSE12.3; I am not sure which release that is): If I boot-up my OpenSuSE through PXELINUX (just loaded kernel and initrd through tftp, the rest of the system still on local hard disk), then the error message is gone.
Looking into the source code of grub2 I found the root cause of the problem:

"grub-core/video/i386/pc/vbe.c" has a function "grub_vbe_enable_mtrr()" which sets a WC MTRR if the framebuffer is not already covered by a MTRR.
It does this on BSP CPU only. So after this code is run, the MTRRs between BSP and APs are inconsistent.